In recent years, there have been increasing demands for higher speed and high-accuracy positioning with respect to an actuator which is to be used for, for example, a table feeder of a machine tool or a conveyor of a semiconductor manufacturing device. Therefore, in many cases, a linear motor is used for, for example, a machine tool or a semiconductor manufacturing device. Moreover, the linear motor is used in direct drive of driving a device without intermediation of a transmission. Thus, as compared to a drive system of converting a rotary mechanism, which is formed of a combination of a rotary servomotor and a ball screw, into a linear motion, there is no degradation in stiffness of the ball screw due to backlash, and high responsiveness can be achieved. Therefore, high speed, high acceleration, and high-accuracy positioning with the linear motor can be achieved.
A related-art linear motor includes a stator and a movable element, which is opposed to the stator while maintaining a certain space and moves relative to the stator. The movable element has a configuration in which a coil is wound around each of teeth of a plurality of segment cores each formed of a magnetic body. The stator includes an iron core formed of a magnetic body and permanent magnets magnetized in a space direction. The permanent magnets are arranged while maintaining a certain distance along a moving direction of the movable element. Moreover, magnetization directions of adjacent permanent magnets are different from each other.
In a conveyor including the above-mentioned linear motor, the number of permanent magnets increases as a moving distance of the movable element increases. Therefore, cost is liable to increase. In order to suppress the increase in cost, the permanent magnets which have hitherto been arranged on the stator are arranged on the teeth of the segment cores of the movable element. Moreover, there has been known a linear motor including a movable element having a configuration in which a coil is wound around each of segment cores and a stator including an iron core having projecting poles (see, for example, Patent Literatures 1 and 2).